The growth of thin films on substrates by hetero-epitaxy is an important manufacturing step in the semiconductor technology. For instance, when native bulk substrates are not available or are too expensive, useful materials are often formed by hetero-epitaxy on seed substrates. Materials grown by hetero-epitaxy have numerous uses. For example, after transfer of the hetero-epitaxial films to another substrate these films can, for instance, be used for epitaxial growth of layers used in electronic and opto-electronic, photovoltaic applications. In the field of light-emitting semiconductor devices or solar cells there is a need to grow heteroepitaxial films of Group III-nitride materials on such substrates as sapphire or SiC.
However, when materials are grown by hetero-epitaxy on substrates on substrates that have lattice constants and coefficients of thermal expansion that are different from the materials being grown, material quality can be compromised by misfit compressive strain leading to generation of dislocations and cracks. Consequently, thin hetero-epitaxial films that are strained due to lattice-parameter misfit can further deteriorate during subsequent steps. Also, films of materials formed by hetero-epitaxy can be grown to only a limited thickness if cracks and dislocations are to be avoided.
However, presently methods used to relax strained hetero-epitaxial films often do not lead to complete lateral relaxation and accordingly do not adequately suppress buckling, the formation of cracks, etc. A method leading to complete or almost complete relaxation of a strained layer formed above a substrate or at least a method that avoids or alleviates the above-mentioned defects would be a useful addition to the art.